Reporter: Tonight, as some of florida's top investigators take another look at the mysterious death of sheena morris, found dead in that hotel shower. The man she was getting ready to marry, who failed that polygraph, has decided to sit down with "20/20." Good to meet you. Nearly five years after he lost his fiancee, joe says he's a victim too. So why sit down with me? Because I have to tell you my side of the story. I'm being victimized cause i cared about someone. I was there for her, when her family a lot of times wasn't. Reporter: Put under the microscope he says by a mother determined to prove her daughter did not commit suicide. The story we've been following for years. Joe says the portrait painted of his relationship with sheena is not a true one. A domestic dispute. We've interviewed a lot of sheena's friends. Many of her friends say that this was a tumultuous relationship. I just don't understand where they're gettin' at. You know -- Reporter: There wasn't any fighting? Well, in a relationship, there's always -- there's always arguments and stuff. Reporter: It was never physical? No. I mean, there was never anything normal -- you know, in a normal relationship, there -- there was fights, there was, you know, back and forths. But there was no -- never any violence, no. Reporter: Nor was there ever any violence with his ex-wife according to joe when we asked him about those battery charges that were dropped. It was a push back and forth. She pushed me, I pushed her back, and then she looked at me and says, "now you're goin' to jail." Reporter: And he points out, his ex wife dropped it all, and he says his fights with sheena, including that one new year's night, were often caused by her jealousy of the family he already had. And he says she was often depressed. Remember that christmas morning video, where kelly sees her daughter smiling and laughing. He sees something else. Remembering the fiancee who couldn't get out of bed that morning, who didn't want to spend christmas, he says, with her family. Reporter: So she -- she wouldn't get out of bed? No. She -- she told me -- she -- she wasn't out of bed for two days, hadn't eaten anything in two days. And she -- Reporter: Was she depressed? I guess she was upset with the fact, or depressed with the fact that -- I was spendin' time with my kids over the holidays. Reporter: And joe says that surprise new year's trip was out of concern for sheena - because she'd been down. I said to myself, maybe we'll just go down there for new year's eve, since we had a crappy new year -- christmas. Reporter: He says she was happy that new years eve night. He remembers too, when she sat there texting her friends from the dinner table. We went out to dinner at the place we were gonna get married at. She was -- with -- talkin' with her family, most -- textin' and talkin' with her family most of the night. Reporter: And he remembers their kiss at midnight. And -- and then new years -- 12:00 came. And we went out on the balcony, and fireworks went off, and you know, we celebrated new years. Reporter: A new year's kiss? Yeah. Exactly, yeah. Everything was great. Reporter: Great, he says. Until he went back inside that hotel room to call his children. To wish them a happy new year, too. And that was it. It lasted all about 15, 20 seconds that I was on the phone. And as I turned back around, she was right there and at that point, she just looked at me and said, "you just up the whole night." Reporter: Why did she have such a big problem with you calling your kids? I don't know. She just didn't want me involved with my children. It was, like, another family to her. And she started getting really upset, screamin' and yellin'. And then she started punchin' the wall. Reporter: Joe says initially it was sheena's idea to leave the hotel but that she suddenly changed her mind. Refusing to go. She actually at one point tried to grab the money that i had on the bureau so and she said that I wasn't leavin'. And I told her, "i am leavin'. We're leavin'." Because at that point, I -- you know, she -- from her punchin' the wall, and screamin' and yellin' the way she did, I -- i was afraid that, you know, cops were gonna come. Reporter: But guests were already placing that call to 911. There's two people over there, just screaming and yelling, a woman and a man, at each other. Reporter: And joe told us what police say he's always told them. And where did you go? Home. Straight home. Straight to my townhouse where there were people there, they were havin' a party, and at least five or six people saw me. Reporter: On the drive home, joe says sheena was on the phone with him suddenly sinking into that depression. What was she saying to you? There was one thing that she did say, and I've made mention in a somber note, if I can't have you to myself, I don't wanna be here. Reporter: Had she ever said that before? Not -- no. Reporter: As for that 911 call sheena made just after 2am -- he just made me bleed and left claw marks all over me and stuff. The scrape on her -- on her finger, we know that came from her punchin' the wall. And the scrape on her neck a small scrape was when she went to grab the money off of the bureau, and -- I grabbed her by her -- shirt, and it -- and it got her necklace. And it -- and left a little scratch on her neck. That's -- that's it. Reporter: He said he was devastated on that new year's day when they all learned sheena was dead. I walk up and I look, what's going on? He looked at me and said I'm sorry for your loss. I just looked at him, I couldn't believe what he said to me. Can we cut? Reporter: When he was rdy to continue. She was a beautiful girl. She was a beautiful girl. I -- this is a tragedy in everybody's lives, you know? Reporter: For you too? Absolutely. I was engaged to her. Reporter: Do you think everybody's forgotten that you felt this way too? No, I just think that they -- they're on the kelley train, and if you go against what kelley says, then you're not an advocate of sheena. Reporter: A grieving mother out for answers no matter the cost? Refusing to accept the possibility that her daughter could have taken her own life? Or a fiance covering his tracks? We've talked to sheena's mother, her family, her friends, and they all categorically say she never would have taken her own life. My personal opinion is nobody ever thinks they're gonna take their own life. Does anybody presume that somebody's gonna take their own life? Reporter: Did she ever say to you that she was depressed, or -- or having suicidal thoughts? She told me she tried to commit suicide when she was 15 years old. Took a bottle of pills. Reporter: In fact that's the same story police say sheena's mother told them the day her body was found. Had there ever been suicidal thoughts before? She had gotten in some trouble with her dad. And, um, and she kinda like said to her father that she took some pills. They checked everything out. She really didn't take anything. It was a false alarm. Reporter: Joe says he understands kelly's need for answers. But says she's looking in the wrong place. But how does he explain the mountain of evidence? The sand on sheena's feet, but no sand in the shower -- her perfect appearance. Her hair, her clothes, and that diamond bracelet on the wrong wrist. I let that the -- professionals deal with that, the investigators and everything else. Reporter: He welcomes this new investigation because he insists he still has nothing to hide. Reporter: And once and for all, did you kill sheena? Absolutely not. And what -- what -- what would be my motive, for god sake? I'm 50 years old. I have three children. Reporter: But what about the polygraph? Why take the test? Because I had nothin' to hide Reporter: How do you explain those test results? Well, I don't. I was uneasy with a lot of the questions he asked first of all. Second of all I was told by a professional the questions that he asked should have never been asked. They were set up questions. But now for joe, there are new questions to answer -- this time from those investigators taking a fresh look at the case, with the real possibility that someone could be charged with murder. Reporter: When was the last time you talked to the investigators on the team? Three weeks ago. Reporter: Were you nervous? Of course I'm nervous. I mean, who wouldn't be nervous?

This transcript has been automatically generated and may not be 100% accurate.

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